\documentclass[12pt,a4paper]{article}

\usepackage{amsmath}      % need for subequations
\usepackage{verbatim}     % useful for program listings
\usepackage{indentfirst}  % useful for the first line indent


\title{Simple \LaTeX document}
\author{Adriana Bratu}
%\date{} commented to show today's date

\begin{document}
\maketitle

\section{First section}
\subsection{Subsection1}

\text{First equation}

\begin{equation}
% \label{egn:i} commented because it was already defined
\sum_{i=1}^n i
\end{equation}

\text{Second equation}

\begin{equation}
\sum_{i=1}^n i^3
\end{equation}

\section{Second section}
\subsection{Items}

\begin{enumerate}
\item This is item1
\item This is item2
\item This is item3
\end{enumerate}

\subsection{Program sample}

\begin{verbatim}
int main(int argc, char** argv){
  int array[n];
  populateData(intarray, n);
  return 0;
}
\end{verbatim}

\end{document}

